This invention relates to novel switch means for electric power tool apparatus holdable by hand during operation.
Power tool apparatus in which the switch means according to the invention can be integrated with special advantage, have been described in my U.S. Pat. Nos. 4,505,170 and 4,619,162; such apparatus consists essentially of
(A) a first building block comprising
(1) an apparatus casing consisting essentially of an elongated assembly having a longitudinal axis and comprising
(1.1) an enveloping shell extending generally in the direction of the said longitudinal axis, and having an open front end and an open rear end; and being of one piece;
(1.2) a first transverse wall extending across the interior of the shell in a region thereof intermediate the said front end and the said rear end axially spaced from both these ends so as to divide the shell interior into a forward chamber and a rearward chamber; the first transverse wall has a throughhole therein and is integral with the said shell;
(1.3) a second transverse wall across the open rear end of the shell and being detachably mounted therein; the second transverse wall has an opening therein; and
(1.4) a speed-reducing unit which is mounted on the second transverse wall on the side thereof facing toward the first transverse wall, and comprises a driven power-transmitting shaft having a driven shaft front end and adapted for fitting into the said throughhole and protruding therefrom into the forward chamber of the shell;
(B) a second, rearward building block comprising
(2) an electric direct current motor comprising, in turn,
(2.1) a motor housing having a central longitudinal axis substantially parallel with the elongated assembly axis, and comprising a surrounding hull, a forward hull end, a rearward hull end wall, and being adapted for having the front end thereof rigidly connected with the second transverse wall on the outside of the latter;
(2.2) driving motor shaft means extending through the interior of the motor housing and being rotatably supported in the opening of the second transverse wall; the driving rotor shaft means have a forward shaft end extend into the rearward shell chamber and are adapted for drivingly engaging the said speed-reducing unit therein; and
(3) insertable bearing-wall means adapted for being mounted transversely in rigid, detachable connection, in the said open front end of the enveloping shell, and having a central axial throughhole; these insertable bearing-wall means comprise
(3.1) shaft-bearing means in the axial throughhole in which a driven power-transmitting shaft of the power tool apparatus can be supported.
An apparatus of the type described hereinbefore has been disclosed by V. Raso and A. C. Eisenhart in their U.S. Pat. No. 3,434,366 granted Mar. 25, 1969.
However, this known apparatus is not intended to be held by hand, especially during operation, but is to be mounted stationary on a solid base 5 on supporting feet 156 (FIG. 1 of U.S. Pat. No. 3,434,366).
If it were adapted to be used by hand it could be used for short tools such as sockets for tightening and loosening nuts or for screwdrivers. However, no heavy duty work could be done with such a power tool, when of reduced size to render it holdable by hand, as the apparatus lacks power-enhancing means such as an impact clutch or the like and could not support the same inside the forward housing of the frame or enveloping sleeve which is only intended to house a gear reduction unit distributed over both the forward and the rearward chamber which are formed in the frame of the Raso et al reduction unit.
A known electrical switch adapted to be mounted on the end part of an electric direct current motor next adjacent the commutator thereof has been described in U.S. Pat. No. 3,681,550 issued on Aug. 1st, 1972 to Perry and Brockelsby. In this known electrical switch, contactor pins 66 extend from a rearward outer plate 62 corresponding to a cap member end wall, infra, in a switch structure through an intermediary cap member 54 into a pivotable brush mounting plate 40 in which there are housed four brushes 47 which are urged with their contractable forward end faces against an insulating wafer 26 having four openings 32 to 35 therein. As the brushes come to register with these openings owing to rotation of the brush mounting plate relative to the wafer, the brushes will penetrate through the openings and come into contact with a conically-shaped surface composed of commutator segments. Flexible wire connections are provided within the brush mounting plate and connect the brushes with the ends of the connector pins lodged in the brush mounting plate.
This known switch is thus of rater complicated structure and suffers from a considerable number of points where the various elements are subject to relatively rapid wear.
In the prior power-tool apparatus known to me, an exchange of impact means or the like present in a forward chamber of the apparatus casing is only provided for by making the forward part of the apparatus casing detachable from the rearward part thereof housing the speed-reducing unit. After the forward apparatus part has been detached, the impact clutch or the like power-transmitting means housed therein can be withdrawn from the forward chamber only by way of the rearward end of the forward part, or, depending on the structure of each casing, part or all of the speed-reducing unit must be removed, before another type of power-transmitting unit can be inserted in that forward chamber.
This is the case in the power tool apparatus described in my U.S. Pat. No. 4,505,170 dated Mar. 19, 1985; in U.S. Pat. No. 4,368,784 to Wunsch et al, granted on Jan. 18, 1983; in German, Offenlegungsschrift DE No. 30 07 630, applied for by Rodac Pneumatic Tools, Carson, Calif., and published on Mar. 12, 1981 (U.S. patent application Ser. No. 70,149 filed on Aug. 27, 1979); in German Offenlegungsschrift DE No. 30 15 423, applied for by Robert Bosch GmbH, Stuttgart, Germany, and published on Oct. 29, 1981; and in Swiss Pat. No. 553,625 granted to Atlas Copco Aktiebolaget, Nacka, Sweden and published on Sept. 13, 1974.